You don't have to write your own popen(), stdio already has one.
Have you actually tried this code? It'll crash, because
That doesn't make a FILE pointer, just an integer pointer, since fd isn't a FILE. You convert a file number into a FILE * with a command like fdopen(fd, "r");
You also forgot to close the end of the pipe you're not using again.
This doesn't work either:
You don't compare strings that way.
...and you have no way to wait for the process on close now, because you didn't store the PID anywhere. stdio popen() can do that and remember, but you can't just from a FILE *.
Honestly I think some review of the C language would do you good before you try to tackle multiprocessing.
Hi
The following is my program to test popen()
routine. The purpose is to print some contents
of the corrent directory.
But in fact, the output is only one character
'a', which I believe is the first char of the file
"a.out".
So, can anybody tell me what is wrong about
this program?... (2 Replies)
hai friends
I have written a tcp chat server in c.. I have designed a cgi program in c to control it... When i try to start the server from the cgi program, it is not starting. Why is that ? I have even tried giving the root ownership for all the programs.. Still its not.
I have used the... (1 Reply)
Hi there,
I'm facing a problem running the tar command with the popen function.
FILE* fp = popen("tar czf - textfile","r")
// output
this program should give the output to the stdout. I don't know if it is possible and which function like fprint() etc. should I use.
I suppose that I... (4 Replies)
hi,
how to work with a background process without a controlling terminal to make use of popen or system call ?
when ever i use popen or system function call in foreground process, there is no problem with respect to that .. but when the same program is run as a background process without a... (7 Replies)
Hello I'm writing a web server in python(obelisk-http.sourceforge.net)
and I'm having a greeat problem with POST method it like that
When someone make a POST request to the server it must open the executable(perl/python/.exe/elf) and send to the STANDART in (stdin) the request and get the... (2 Replies)
Hi!
I'm trying to write a c program. The child process must transmit to the parent a file name and the parent must count the lines from the file and return te result to the child. Here is what i've done. It doesn't stop running, I guess. I'm sorry if it's an ugly code, i'm new at this stuff,... (2 Replies)
Hi
I am trying to use popen function with wrtie option to give inputs to ftp command.
#include "stdio.h"
int main(int argv ,char *argc)
{
int size=0;
char *buf;
FILE *fp;
fp = popen("ftp","w");
while(getline(&buf,&size,stdin) != -1)
write(fp,buf);... (0 Replies)
hi,
i am trying to use popen to run a grep process and check if the pattern exists in the file that i am searching in. i am getting segmentation fault when i try to execute the following code
char *cd;
char flag;
char hdr_flpsp;
char hdr_flpsp2;
FILE *fp;
printf ("program starts");... (1 Reply)
in man system it talks about SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
Does this signal stuff also happen in popen command?
(even though man popen says nothing about signals)
also if I am not using wait(&status) and I am using waitpid(pid, NULL, 0)
how would... (1 Reply)
Hello all,
I am reading a huge zip file in POPEN process and then writting that to a normal file which of 2GB. Now the process is failing when I looked for the cause someother process comming in after I read my file and it is deleting the zip. But in theory the popen command should read the... (5 Replies)
Discussion started by: arunkumar_mca
5 Replies
LEARN ABOUT OSF1
popen
popen(3) Library Functions Manual popen(3)NAME
popen - Initiates a pipe to a process
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <stdio.h>
FILE *popen (
const char *command,
const char *type );
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
popen(): XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Points to a null-terminated string containing a shell command line. Points to a null-terminated string containing an I/O mode.
DESCRIPTION
The popen() function creates a pipe between the calling program and a shell command to be executed. It returns a pointer to a FILE struc-
ture for the stream.
If the type parameter is the value r, the calling program can read from the standard output of the command by reading from the returned
file stream. If the type parameter is the value w, the calling program can write to the standard input of the command by writing to the
returned file stream.
Because open files are shared, a type r command can be used as an input filter and a type w command as an output filter.
NOTES
Programs using the popen() function to invoke an output filter should beware of possible deadlock caused by output data remaining in the
program's buffer. This can be avoided by either using the setbuf() function to ensure that the output stream is unbuffered, or by using
the fflush() function to ensure that all buffered data is flushed before calling the pclose() function. If the original processes and the
process started with the popen() function concurrently read or write a common file, neither should use buffered I/O. If they do, the
results are unpredictable.
RETURN VALUES
Upon successful completion, the popen() function returns a pointer to the FILE structure for the opened stream. In case of error because
files or processes could not be created, the popen() function returns a null pointer.
RELATED INFORMATION
Functions: exec(2), fork(2), fclose(3), fopen(3), pclose(3), pipe(2), setbuf(3)
Standards: standards(5) delim off
popen(3)